Leptin-induced growth of human ZR-75-1 breast cancer cells is associated with up-regulation of cyclin D1 and c-Myc and down-regulation of tumor suppressor p53 and p21WAF1/CIP1

Obesity and cancer: focus on leptin

Over the past decades, obesity has grown to epidemic proportions worldwide. It has been associated with an increased risk for different types of cancer. In addition, obesity has been associated with a poor prognosis, an increased risk of metastasis and mortality, and resistance to anti-cancer therapies. The pathophysiological mechanisms underlying the obesity-cancer connection have not yet been fully elucidated. However, this connection could result, at least in part, from the action of adipokines, whose levels are increased in obesity. Among these adipokines, evidence suggests leptin's critical role in linking obesity to cancer. In this review, we first summarize the current state of the literature regarding the implication of leptin in tumorigenic processes. Next, we focus on the effects of leptin on the anti-tumor immune response. Then, we discuss the influence of leptin on the efficiency of antineoplastic treatments and the development of tumor resistance. Finally, we highlight the use of leptin as a potential target for the prevention and treatment of cancer.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Obesity: a perfect storm for carcinogenesis

Obesity-related cancers account for 40% of the cancer cases observed in the USA and obesity is overtaking smoking as the most widespread modifiable risk factor for carcinogenesis. Here, we use the hallmarks of cancer framework to delineate how obesity might influence the carcinogenic hallmarks in somatic cells. We discuss the effects of obesity on (a) sustaining proliferative signaling; (b) evading growth suppressors; (c) resisting cell death; (d) enabling replicative immortality; (e) inducing angiogenesis; (f) activating invasion and metastasis; (g) reprogramming energy metabolism; and (h) avoiding immune destruction, together with its effects on genome instability and tumour-promoting inflammation. We present the current understanding and controversies in this evolving field, and highlight some areas in need of further cross-disciplinary focus. For instance, the relative importance of the many potentially causative obesity-related factors is unclear for each type of malignancy. Even within a single tumour type, it is currently unknown whether one obesity-related factor consistently plays a predominant role, or if this varies between patients or, even in a single patient with time. Clarifying how the hallmarks are affected by obesity may lead to novel prevention and treatment strategies for the increasingly obese population.

SIRT1 Mediates Neuroprotective and Neurorescue Effects of Camel α-Lactalbumin and Oleic Acid Complex on Rotenone-Induced Parkinson's Disease

Parkinson's disease (PD) is the second most common devastating neurodegenerative disorder. Presently used therapies for PD have severe side effects and are limited to only temporary improvement. Therefore, a new therapeutic approach to treat PD urgently needs to be developed. α-Lactalbumin, the most abundant milk protein in camel milk, has been attributed to various medicinal properties. This study intended to investigate the neuroprotective efficacy of the camel α-lactalbumin and oleic acid (CLOA) complex. One mechanism postulated to underlie neuroprotection by the CLOA complex is the induction of silent information regulatory protein (SIRT1). SIRT1 is known to be involved in several pathological and physiological processes, and it has been suggested that SIRT1 plays a protective role in PD. Oxidative stress, inflammation, mitochondrial dysfunction, and apoptosis are involved in PD pathogenesis. Our results revealed that SIRT1 inhibits oxidative stress by maintaining HIF-1α in a deacetylated state. SIRT1 upregulates the expression of FOXO3a and HSF-1, thus inhibiting apoptosis and maintaining the homeostasis of cellular proteins. Increased SIRT1 expression reduces the levels of TNF-α, IL-6, and IL-8, which in turn inhibits neuroinflammation. In addition to SIRT1, the CLOA complex also enhances the expression of survivin and leptin and promotes the survival of neuroblastoma cells. Altogether, our results suggest that the CLOA complex might be a novel therapeutic molecule that could ameliorate neuronal cell damage in PD.

Prognostic impact of body mass index (BMI) in HER2+ breast cancer treated with anti-HER2 therapies: from preclinical rationale to clinical implications

Human Epidermal growth factor Receptor 2 (HER2) overexpression or HER2 gene amplification defines a subset of breast cancers (BCs) characterized by higher biological and clinical aggressiveness. The introduction of anti-HER2 drugs has remarkably improved clinical outcomes in patients with both early-stage and advanced HER2+ BC. However, some HER2+ BC patients still have unfavorable outcomes despite optimal anti-HER2 therapies. Retrospective clinical analyses indicate that overweight and obesity can negatively affect the prognosis of patients with early-stage HER2+ BC. This association could be mediated by the interplay between overweight/obesity, alterations in systemic glucose and lipid metabolism, increased systemic inflammatory status, and the stimulation of proliferation pathways resulting in the stimulation of HER2+ BC cell growth and resistance to anti-HER2 therapies. By contrast, in the context of advanced disease, a few high-quality studies, which were included in a meta-analysis, showed an association between high body mass index (BMI) and better clinical outcomes, possibly reflecting the negative prognostic role of malnourishment and cachexia in this setting. Of note, overweight and obesity are modifiable factors. Therefore, uncovering their prognostic role in patients with early-stage or advanced HER2+ BC could have clinical relevance in terms of defining subsets of patients requiring more or less aggressive pharmacological treatments, as well as of designing clinical trials to investigate the therapeutic impact of lifestyle interventions aimed at modifying body weight and composition. In this review, we summarize and discuss the available preclinical evidence supporting the role of adiposity in modulating HER2+ BC aggressiveness and resistance to therapies, as well as clinical studies reporting on the prognostic role of BMI in patients with early-stage or advanced HER2+ BC.

Tumor Metabolic Reprogramming by Adipokines as a Critical Driver of Obesity-Associated Cancer Progression

Adiposity is associated with an increased risk of various types of carcinoma. One of the plausible mechanisms underlying the tumor-promoting role of obesity is an aberrant secretion of adipokines, a group of hormones secreted from adipose tissue, which have exhibited both oncogenic and tumor-suppressing properties in an adipokine type- and context-dependent manner. Increasing evidence has indicated that these adipose tissue-derived hormones differentially modulate cancer cell-specific metabolism. Some adipokines, such as leptin, resistin, and visfatin, which are overproduced in obesity and widely implicated in different stages of cancer, promote cellular glucose and lipid metabolism. Conversely, adiponectin, an adipokine possessing potent anti-tumor activities, is linked to a more favorable metabolic phenotype. Adipokines may also play a pivotal role under the reciprocal regulation of metabolic rewiring of cancer cells in tumor microenvironment. Given the fact that metabolic reprogramming is one of the major hallmarks of cancer, understanding the modulatory effects of adipokines on alterations in cancer cell metabolism would provide insight into the crosstalk between obesity, adipokines, and tumorigenesis. In this review, we summarize recent insights into putative roles of adipokines as mediators of cellular metabolic rewiring in obesity-associated tumors, which plays a crucial role in determining the fate of tumor cells.

The Role of Adipokines and Bone Marrow Adipocytes in Breast Cancer Bone Metastasis

The morbidity and mortality of breast cancer is mostly due to a distant metastasis, especially to the bone. Many factors may be responsible for bone metastasis in breast cancer, but interactions between tumor cells and other surrounding types of cells, and cytokines secreted by both, are expected to play the most important role. Bone marrow adipocyte (BMA) is one of the cell types comprising the bone, and adipokine is one of the cytokines secreted by both breast cancer cells and BMAs. These BMAs and adipokines are known to be responsible for cancer progression, and this review is focused on how BMAs and adipokines work in the process of breast cancer bone metastasis. Their potential as suppressive targets for bone metastasis is also explored in this review.

Diallyl Trisulfide Inhibits Leptin-induced Oncogenic Signaling in Human Breast Cancer Cells but Fails to Prevent Chemically-induced Luminal-type Cancer in Rats

Previous studies have demonstrated inhibitory effect of garlic component diallyl trisulfide (DATS) on growth of breast cancer cells in vitro and in vivo. This study investigated the effect of DATS on oncogenic signaling regulated by leptin, which plays an important role in breast carcinogenesis. Leptin-induced phosphorylation and nuclear translocation of STAT3 was inhibited significantly in the presence of DATS in MCF-7 (a luminal-type human breast cancer cell line) and MDA-MB-231 (a basal-like human breast cancer cell line). Leptin-stimulated cell proliferation, clonogenic cell survival, and migration and/or invasion ability in MCF-7 and/or MDA-MB-231 cells were also suppressed by DATS treatment. DATS exposure resulted in inhibition of leptin-stimulated expression of protein and/or mRNA levels of Bcl-2, Bcl-xL, Cyclin D1, vascular endothelial growth factor, and matrix metalloproteinase-2. Western blotting revealed a decrease in protein levels of phosphorylated STAT3 in breast cancer xenografts from DATS-treated mice when compared to controls in vivo. However, the incidence of N-methyl-N-nitrosourea-induced luminal-type breast cancer development in rats was not affected by oral administration of 5 mg/kg or 25 mg/kg DATS. The present study reveals that oncogenic signaling induced by leptin is inhibited in the presence of DATS but higher doses of this phytochemical may be required to achieve chemopreventive activity.

Leptin, Adiponectin, and Sam68 in Bone Metastasis from Breast Cancer

The most serious aspect of neoplastic disease is the spread of cancer cells to secondary sites. Skeletal metastases can escape detection long after treatment of the primary tumour and follow-up. Bone tissue is a breeding ground for many types of cancer cells, especially those derived from the breast, prostate, and lung. Despite advances in diagnosis and therapeutic strategies, bone metastases still have a profound impact on quality of life and survival and are often responsible for the fatal outcome of the disease. Bone and the bone marrow environment contain a wide variety of cells. No longer considered a passive filler, bone marrow adipocytes have emerged as critical contributors to cancer progression. Released by adipocytes, adipokines are soluble factors with hormone-like functions and are currently believed to affect tumour development. Src-associated in mitosis of 68 kDa (Sam68), originally discovered as a protein physically associated with and phosphorylated by c-Src during mitosis, is now recognised as an important RNA-binding protein linked to tumour onset and progression of disease. Sam68 also regulates splicing events and recent evidence reports that dysregulation of these events is a key step in neoplastic transformation and tumour progression. The present review reports recent findings on adipokines and Sam68 and their role in breast cancer progression and metastasis.

Methylenetetrahydrofolate Dehydrogenase 1 (MTHFD1) is Underexpressed in Clear Cell Renal Cell Carcinoma Tissue and Transfection and Overexpression in Caki-1 Cells Inhibits Cell Proliferation and Increases Apoptosis

Background

The aims of this study were to investigate the expression of methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) in human tissue containing clear cell renal cell carcinoma (CCRCC) compared with normal renal tissue, and the effects of upregulating the expression of MTHFD1 in the human CCRCC cell line, Caki-1.

Material/Methods

Tumor and adjacent normal renal tissue were obtained from 44 patients who underwent radical nephrectomy for CCRCC. Caki-1 human CCRCC cells were divided into the control group, the empty vector (EV) group, and the plasmid-treated group that overexpressed MTHFD1. MTHFD1 mRNA and protein levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. The cell counting kit-8 (CCK-8) assay measured cell viability. Flow cytometry evaluated apoptosis and the cell cycle. Western blot measured the protein levels of MTHFD1, Bax, Bcl-2, Akt, p53, and cyclin D1, and qRT-PCR determined the gene expression profiles.

Results

MTHFD1 mRNA and protein levels in CCRCC tumor tissues were significantly lower compared with adjacent normal renal tissue. MTHFD1 over-expression in Caki-1 cells inhibited cell proliferation, arrested cells in the G1 phase, increased cell apoptosis, and upregulated gene and protein expression of Bax/Bcl-2 and p53, and inhibited p-Akt, and cyclin D1.

Conclusions

MTHFD1 was underexpressed in CCRCC tissue when compared with normal renal tissue. MTHFD1 transfection of human CCRCC Caki-1 cells in vitro inhibited cell proliferation and promoted apoptosis, associated with reduced expression of cyclin D1, reduced Akt phosphorylation, and increased expression of Bax/Bcl-2 and p53.

Adipokines as therapeutic targets in breast cancer treatment

INTRODUCTION

Adipocytes, which represent a substantial part of the tumor microenvironment in breast cancer, secrete several adipokines that affect tumorigenesis, cancer progression, metastasis, and treatment resistance via multiple signaling pathways. Areas covered: In this review, we focus on the role of leptin, adiponectin, autotaxin, and interleukin-6 in breast cancer initiation, progression, metastasis, and drug response. Furthermore, we investigated adipokines as potential targets of breast cancer-specific drugs. Expert opinion: Adipokines and adipokine receptors are deregulated in breast cancer. Adipokines play various roles in breast cancer initiation, progression, metastasis, and drug response, hence, adipokine signaling could be an effective drug target. Several clinical trials are in progress to test the efficacy of adipokine targeting agents. However, adipokines also affect metabolic homeostasis; hence, the adverse effects of the targeted drug should be investigated and addressed.

Leptin regulation of the p53-HIF1α/PKM2-aromatase axis in breast adipose stromal cells: a novel mechanism for the obesity-breast cancer link

BACKGROUND/OBJECTIVES

Obesity (body mass index (BMI)⩾30 kg m-2) is associated with an increased risk of estrogen-dependent breast cancer after menopause. Levels of aromatase, the rate-limiting enzyme in estrogen biosynthesis, are elevated in breast tissue of obese women. Recently, the regulation of aromatase by the p53-hypoxia-inducible factor-1α (HIF1α)/pyruvate kinase M2 (PKM2) axis was characterized in adipose stromal cells (ASCs) of women with Li-Fraumeni Syndrome, a hereditary cancer syndrome that predisposes to estrogen-dependent breast cancer. The current study aimed to determine whether stimulation of aromatase by obesity-associated adipokine leptin involves the regulation of the p53-HIF1α/PKM2 axis.

SUBJECTS/METHODS

Human breast ASCs were used to characterize the p53-HIF1α/PKM2-aromatase axis in response to leptin. The effect of pharmacological or genetic modulation of protein kinase C (PKC), mitogen-activated protein kinase (MAPK), p53, Aha1, Hsp90, HIF1α and PKM2 on aromatase promoter activity, expression and enzyme activity was examined. Semiquantitative immunofluorescence and confocal imaging were used to assess ASC-specific protein expression in formalin-fixed paraffin-embedded tissue sections of breast of women and mammary tissue of mice following a low-fat (LF) or high-fat (HF) diet for 17 weeks.

RESULTS

Leptin-mediated induction of aromatase was dependent on PKC/MAPK signaling and the suppression of p53. This, in turn, was associated with an increase in Aha1 protein expression, activation of Hsp90 and the stabilization of HIF1α and PKM2, known stimulators of aromatase expression. Consistent with these findings, ASC-specific immunoreactivity for p53 was inversely associated with BMI in breast tissue, while HIF1α, PKM2 and aromatase were positively correlated with BMI. In mice, HF feeding was associated with significantly lower p53 ASC-specific immunoreactivity compared with LF feeding, while immunoreactivity for HIF1α, PKM2 and aromatase were significantly higher.

CONCLUSIONS

Overall, findings demonstrate a novel mechanism for the obesity-associated increase in aromatase in ASCs of the breast and support the study of lifestyle interventions, including weight management, which may reduce breast cancer risk via effects on this pathway.

Down Syndrome, Obesity, Alzheimer's Disease, and Cancer: A Brief Review and Hypothesis

Down syndrome (trisomy 21), a complex mix of physical, mental, and biochemical issues, includes an increased risk of Alzheimer’s disease and childhood leukemia, a decreased risk of other tumors, and a high frequency of overweight/obesity. Certain features related to the third copy of chromosome 21 (which carries the APP gene and several anti-angiogenesis genes) create an environment favorable for Alzheimer’s disease and unfavorable for cancer. This environment may be enhanced by two bioactive compounds from fat cells, leptin, and adiponectin. This paper outlines these fat-related disease mechanisms and suggests new avenues of research to reduce disease risk in Down syndrome.

Synergistic anticancer effects of ruxolitinib and calcitriol in estrogen receptor‑positive, human epidermal growth factor receptor 2‑positive breast cancer cells

The Janus kinase (JAK)1 and JAK2 inhibitor, ruxolitinib, and the active form of vitamin D (calcitriol) were previously reported to possess anticancer effects in breast cancer. The present study investigated the combined effects of ruxolitinib and calcitriol on an estrogen receptor (ER)‑positive, human epidermal growth factor receptor 2 (HER2)‑positive, breast cancer cell line. The ER and HER2‑positive MCF7‑HER18 breast cancer cell line was used to investigate the combination effect of ruxolitinib and calcitriol. A bromodeoxyuridine (BrdU) assay was used to investigate cell growth inhibition. The synergism of this combination therapy was examined using the Chou‑Talalay method. Cell cycle analysis was performed by flow cytometry, and apoptosis was evaluated by flow cytometry following Annexin V‑fluorescein isothiocyanate (FITC) and propidium iodide (PI) staining. Alterations in protein expression levels were analyzed by western blotting. The BrdU assay indicated that combination treatment using ruxolitinib and calcitriol produced a synergistic anti‑proliferative effect in MCF7‑HER18 breast cancer cells. Annexin V‑FITC/PI staining and cell cycle analysis identified a synergistic increase in apoptosis and sub‑G1 arrest in the presence of ruxolitinib and calcitriol. Western blot analysis revealed that these synergistic effects of ruxolitinib and calcitriol were associated with reduced protein levels of JAK2, phosphorylated JAK2, c‑Myc proto oncogene protein, cyclin‑D1, apoptosis regulator Bcl‑2 and Bcl‑2‑like protein 1, and with increased levels of caspase‑3 and Bcl‑2‑associated agonist of cell death proteins. The results of the present study demonstrated the synergistic anticancer effects of ruxolitinib and calcitriol in ER and HER2‑positive MCF7‑HER18 breast cancer cells. Based on these findings, ruxolitinib and calcitriol may have potential as a combination therapy for patients with ER and HER2‑positive breast cancer.

Novel leptin OB3 peptide-induced signaling and progression in thyroid cancers: Comparison with leptin

Obesity results in increased secretion of cytokines from adipose tissue and is a risk factor for various cancers. Leptin is largely produced by adipose tissue and cancer cells. It induces cell proliferation and may serve to induce various cancers. OB3-leptin peptide (OB3) is a new class of functional leptin peptide. However, its mitogenic effect has not been determined. In the present study, because of a close link between leptin and the hypothalamic-pituitary-thyroid axis, OB3 was compared with leptin in different thyroid cancer cells for gene expression, proliferation and invasion. Neither agent stimulated cell proliferation. Leptin stimulated cell invasion, but reduced adhesion in anaplastic thyroid cancer cells. Activated ERK1/2 and STAT3 contributed to leptin-induced invasion. In contrast, OB3 did not affect expression of genes involved in proliferation and invasion. In vivo studies in the mouse showed that leptin, but not OB3, significantly increased circulating levels of thyrotropin (TSH), a growth factor for thyroid cancer. In summary, OB3 is a derivative of leptin that importantly lacks the mitogenic effects of leptin on thyroid cancer cells.

Estrogen receptor signaling mediates leptin-induced growth of breast cancer cells via autophagy induction

Leptin, a hormone derived from adipose tissue, promotes growth of cancer cells via multiple mechanisms. Estrogen receptor signaling is also known to stimulate the growth of breast cancer cells. However, the involvement of estrogen receptor signaling in the oncogenic actions of leptin and its underlying mechanisms are not clearly understood. Herein, we investigated mechanisms for estrogen receptor signaling-mediated growth of breast cancer cells, particularly focusing on autophagy, which plays a crucial role in leptin-induced tumor growth. Inhibition of estrogen receptor signaling via gene silencing or treatment with a pharmacological inhibitor (tamoxifen) abolished leptin-induced growth of MCF-7 human breast cancer cells. Interestingly, leptin-induced autophagy activation, determined by up-regulation of autophagy-related genes and autophagosome formation, was also significantly suppressed by inhibiting estrogen receptor signaling. Moreover, inhibition of estrogen receptor markedly prevented leptin-induced activation of AMPK/FoxO3A axis, which plays a crucial role in autophagy induction. Leptin-induced cell cycle progression and Bax down-regulation were also prevented by treatment with tamoxifen. The pivotal roles of estrogen receptor signaling in leptin-induced cell cycle progression, apoptosis suppression, and autophagy induction were further confirmed in MCF-7 tumor xenograft model. Taken together, these results demonstrate that estrogen receptor signaling plays a key role in leptin-induced growth of breast cancer cells via autophagy activation.

Immunohistochemical staining of leptin is associated with grade, stage, lymph node involvement, recurrence, and hormone receptor phenotypes in breast cancer

Background

Obesity is part of the established risk factors for breast cancer (BC) in postmenopausal females. Circulating leptin increases in parallel with the increase of body weight and fat reservoir.

Methods

This research investigated the link between leptin phenotype and the clinicopathological factors in BC. A large set of breast cancer cases (449), and 27 non-cancerous tissue samples of breast were employed for leptin expression recognition using immunohistochemistry staining.

Results

Cytoplasmic immunohistochemical staining of leptin was recognized in 376 (83.7%) and 25 (92.6%) of BC and control cases respectively. Leptin immunostaining were significantly associated with age, histotypes, grade, stage, lymph node involvement, tumor recurrence, hormone receptor phenotypes, ER and HER2 expressions, and p-values were (P = 0.0233), (P = 0.0001), (P = 0.050), (P = 0.0291), (P = 0.0300), (P = 0.0023), (P = 0.0021), (P = 0.0279) respectively. Reasonable proportion of cases with low staining score was more prevalent in all subgroups of clinicopathological parameters except ER- PR+ HER2- hormone receptor phenotype and mucinous carcinoma which showed high level of leptin immunoreactivity. Tumor recurrence is less prevailing in high score leptin immunostaining cases. Furthermore, Log Rank (Mantel-Cox) test findings revealed considerably different survival distributions were observed for the different categories of leptin immunostaining scores (P = 0.032). Negative leptin immunostaining is related to poor survival.

Conclusions

Our preliminary findings support leptin clinical value in confirming BC diagnosis as well as prognosis. These results suggest that leptin molecule is an important biomarker that could identify type, grade, stage, lymph node involvement, relapse and prognosis in breast cancer.

Expression of AdipoR1 and AdipoR2 Receptors as Leptin-Breast Cancer Regulation Mechanisms

The development of breast cancer is influenced by the adipose tissue through the proteins leptin and adiponectin. However, there is little research concerning AdipoR1 and AdipoR2 receptors and the influence of leptin over them. The objective of this work was to analyze the expression of AdipoR1 and AdipoR2, modulated by differential concentrations of leptin in an obesity model (10 ng/mL, 100 ng/mL, and 1000 ng/mL) associated with breast cancer in MCF-7 and HCC1937 cell lines. Each cell line was characterized through immunohistochemistry, and the expression of AdipoR1 and AdipoR2 was analyzed by PCR in real time using TaqMan® probes. Leptin induced an increase in cell population of MCF-7 (23.8%, 10 ng/mL, 48 h) and HCC1937 (17.24%, 1000 ng/mL, 72 h). In MCF-7, the expression of AdipoR1 decreased (3.81%, 1000 ng/mL) and the expression of AdipoR2 increased by 13.74 times (10 ng/mL) with regard to the control. In HCC1937, the expression of AdipoR1 decreased by 86.28% (10 ng/mL), as well as the expression of AdipoR2 (50.3%, 100 ng/mL). In regard to the results obtained, it could be concluded that leptin has an effect over the expression of AdipoR1 and AdipoR2 mRNA.

Leptin receptor signaling via Janus kinase 2/Signal transducer and activator of transcription 3 impacts on ovarian cancer cell phenotypes

Ovarian cancer is a leading cause of cancer mortality in women world-wide. Considerable progress has been made to characterize the different subtypes of ovarian cancer, but specific therapies remain limited and prognosis poor. Cytokine signaling via the interleukin-6 receptor (IL-6R) family and related receptors has been implicated in a number of cancers, including those with an ovarian origin. The leptin receptor (LEPR) is structurally related to these receptors and utilizes similar downstream pathways. LEPR has diverse roles in metabolism, appetite and bone formation with obesity linked to both elevated levels of leptin and increased cancer incidence. This study investigated a potential role for LEPR signaling in ovarian cancer. Leptin stimulation led to increased proliferation, survival and migration of LEPR-expressing ovarian cancer cell lines, with the effects shown to be mediated by the downstream Janus kinase 2/Signal transducer and activator of transcription 3 (JAK2/STAT3) pathway. A significant correlation was identified between high co-expression of leptin and LEPR and decreased patient survival. This study collectively suggests that leptin/LEPR signaling via JAK2/STAT3 has the potential to significantly impact on pathogenesis in a subset of ovarian cancer patients who may benefit from strategies that dampen this pathway.

Leptin OB3 peptide suppresses leptin-induced signaling and progression in ovarian cancer cells

BACKGROUND

Obesity and its comorbidities constitute a serious health burden worldwide. Leptin plays an important role in diet control; however, it has a stimulatory potential on cancer cell proliferation. The OB3 peptide, a synthetic peptide, was shown to be more active than leptin in regulating metabolism but with no mitogenic effects in cancer cells.

METHODS

In this study, we investigated the proliferative effects, gene expressions and signaling pathways modulated by leptin and OB3 in human ovarian cancer cells. In addition, an animal study was performed.

RESULTS

Leptin, but not OB3, induced the proliferation of ovarian cancer cells. Interestingly, OB3 blocked the leptin-induced proliferative effect when it was co-applied with leptin. Both leptin and OB3 activated the phosphatidylinositol-3-kinase (PI3K) signal transduction pathway. In addition, leptin stimulated the phosphorylation of signal transducer and activator of transcription-3 (STAT3) Tyr-705 as well as estrogen receptor (ER)α, and the expression of ERα-responsive genes. Interestingly, all leptin-induced signal activation and gene expressions were blocked by the co-incubation with OB3 and the inhibition of extracellular signal-regulated kinase (ERK)1/2. Coincidently, leptin, but not OB3, increased circulating levels of follicle-stimulating hormone (FSH) which is known to play important roles in the initiation and proliferation of ovarian cancer cells.

CONCLUSIONS

In summary, our findings suggest that the OB3 peptide may prevent leptin-induced ovarian cancer initiation and progression by disrupting leptin-induced proliferative signals via STAT3 phosphorylation and ERα activation. Therefore, the OB3 peptide is a potential anticancer agent that might be employed to prevent leptin-induced cancers in obese people.

The molecular mechanism of action of superactive human leptin antagonist (SHLA) and quadruple leptin mutein Lan-2 on human ovarian epithelial cell lines

Introduction

A number of leptin receptor antagonists have been synthesised for therapeutic use, with pre-clinical tests suggesting their future use in anticancer therapy. To our knowledge, there are no data concerning the possible application of leptin receptor blockers in ovarian cancer.

Methods

In this study, we evaluated two leptin receptor antagonists: superactive human leptin antagonist (SHLA) and quadruple leptin mutein, Lan-2 (L39A/D40A/F41A/I42A), on cell proliferation (Alamar Blue test, BrdU assay), cell cycle gene (qPCR) and protein expression (Western blot) and cell signalling pathways (Western blot) in three different types of cell lines: OVCAR-3, CaOV-3 and HOSEpiC.

Results

Both receptor blockers had no effect on non-cancerous HOSEpiC cell line proliferation; however, both reversed the stimulatory effect of leptin on CaOV-3 cell line proliferation to control levels and to below control levels in OVCAR-3 cells. In metastatic carcinoma CaOV-3, both ObR antagonists had an inhibitory effect on the cdk2/cyclin D1 complex, while in serous carcinoma, OVCAR-3, they only had an effect on cdk2 and cdk4 protein expression. SHLA had an inhibitory effect on all investigated signalling pathways in OVCAR-3, while only on Stat3 in CaOV-3. Lan-2 had an inhibitory effect on Stat3 and ERK1/2 in CaOV-3, while in OVCAR-3 it only affected Akt protein phosphorylation.

Conclusion

Based on these results, we conclude that SHLA and Lan-2 are promising leptin receptor inhibitors which could be used to block leptin activity, eliminating its negative effects on activities related to carcinogenesis. However, the selection of a specific antagonist should be related to tumour type.

Activated FXR Inhibits Leptin Signaling and Counteracts Tumor-promoting Activities of Cancer-Associated Fibroblasts in Breast Malignancy

Cancer-associated fibroblasts (CAFs), the principal components of the tumor stroma, play a central role in cancer development and progression. As an important regulator of the crosstalk between breast cancer cells and CAFs, the cytokine leptin has been associated to breast carcinogenesis. The nuclear Farnesoid X Receptor-(FXR) seems to exert an oncosuppressive role in different tumors, including breast cancer. Herein, we demonstrated, for the first time, that the synthetic FXR agonist GW4064, inhibiting leptin signaling, affects the tumor-promoting activities of CAFs in breast malignancy. GW4064 inhibited growth, motility and invasiveness induced by leptin as well as by CAF-conditioned media in different breast cancer cell lines. These effects rely on the ability of activated FXR to increase the expression of the suppressor of the cytokine signaling 3 (SOCS3) leading to inhibition of leptin-activated signaling and downregulation of leptin-target genes. In vivo xenograft studies, using MCF-7 cells alone or co-injected with CAFs, showed that GW4064 administration markedly reduced tumor growth. Interestingly, GW4064-treated tumors exhibited decreased levels of leptin-regulated proteins along with a strong staining intensity for SOCS3. Thus, FXR ligands might represent an emerging potential anti-cancer therapy able to block the tumor supportive role of activated fibroblasts within the breast microenvironment.

Autophagy induction by leptin contributes to suppression of apoptosis in cancer cells and xenograft model: involvement of p53/FoxO3A axis

Leptin, a hormone mainly produced from adipose tissue, has been shown to induce proliferation of cancer cells. However, the molecular mechanisms underlying leptin-induced tumor progression have not been clearly elucidated. In the present study, we investigated the role of autophagy in leptin-induced cancer cell proliferation using human hepatoma (HepG2) and breast cancer cells (MCF-7), and tumor growth in a xenograft model. Herein, we showed that leptin treatment caused autophagy induction as assessed by increase in expression of autophagy-related genes, including beclin-1, Atg5 and LC3 II, further induction of autophagosome formation and autophagic flux. Interestingly, inhibition of autophagic process by treatment with inhibitors and LC3B gene silencing blocked leptin-induced increase in cell number and suppression of apoptosis, indicating a crucial role of autophagy in leptin-induced tumor progression. Moreover, gene silencing of p53 or FoxO3A prevented leptin-induced LC3 II protein expression, suggesting an involvement of p53/FoxO3A axis in leptin-induced autophagy activation. Leptin administration also accelerated tumor growth in BALB/c nude mice, which was found to be autophagy dependent. Taken together, our results demonstrate that leptin-induced tumor growth is mediated by autophagy induction and autophagic process would be a promising target to regulate development of cancer caused by leptin production.

Adiposity is associated with p53 gene mutations in breast cancer

Mutations in the p53 gene are among the most frequent genetic events in human cancer and may be triggered by environmental and occupational exposures. We examined the association of clinical and pathological characteristics of breast tumors and breast cancer risk factors according to the prevalence and type of p53 mutations. Using tumor blocks from incident cases from a case-control study in western New York, we screened for p53 mutations in exons 2-11 using the Affymetrix p53 Gene Chip array and analyzed case-case comparisons using logistic regression. The p53 mutation frequency among cases was 28.1 %; 95 % were point mutations (13 % of which were silent) and the remainder were single base pair deletions. Sixty seven percent of all point mutations were transitions; 24 % of them are G:C>A:T at CpG sites. Positive p53 mutation status was associated with poorer differentiation (OR, 95 % CI 2.29, 1.21-4.32), higher nuclear grade (OR, 95 % CI 1.99, 1.22-3.25), and increased Ki-67 status (OR, 95 % CI 1.81, 1.10-2.98). Cases with P53 mutations were more likely to have a combined ER-positive and PR-negative status (OR, 95 % CI 1.65, 1.01-2.71), and a combined ER-negative and PR-negative status (OR, 95 % CI 2.18, 1.47-3.23). Body mass index >30 kg/m(2), waist circumference >79 cm, and waist-to-hip ratio >0.86 were also associated with p53 status; obese breast cancer cases are more likely to have p53 mutations (OR, 95 % CI 1.78, 1.19-2.68). We confirmed that p53 mutations are associated with less favorable tumor characteristics and identified an association of p53 mutation status and adiposity.

Leptin produced by obese adipose stromal/stem cells enhances proliferation and metastasis of estrogen receptor positive breast cancers

Introduction

The steady increase in the incidence of obesity among adults has been paralleled with higher levels of obesity-associated breast cancer. While recent studies have suggested that adipose stromal/stem cells (ASCs) isolated from obese women enhance tumorigenicity, the mechanism(s) by which this occurs remains undefined. Evidence suggests that increased adiposity results in increased leptin secretion from adipose tissue, which has been shown to increased cancer cell proliferation. Previously, our group demonstrated that ASCs isolated from obese women (obASCs) also express higher levels of leptin relative to ASCs isolated from lean women (lnASCs) and that this obASC-derived leptin may account for enhanced breast cancer cell growth. The current study investigates the impact of inhibiting leptin expression in lnASCs and obASCs on breast cancer cell (BCC) growth and progression.

Methods

Estrogen receptor positive (ER+) BCCs were co-cultured with leptin shRNA lnASCs or leptin shRNA obASCs and changes in the proliferation, migration, invasion, and gene expression of BCCs were investigated. To assess the direct impact of leptin inhibition in obASCs on BCC proliferation, MCF7 cells were injected alone or mixed with control shRNA obASCs or leptin shRNA obASCs into SCID/beige mice.

Results

ER+ BCCs were responsive to obASCs during direct co-culture, whereas lnASCs were unable to increase ER⁺ BCC growth. shRNA silencing of leptin in obASCs negated the enhanced proliferative effects of obASC on BCCs following direct co-culture. BCCs co-cultured with obASCs demonstrated enhanced expression of epithelial-to-mesenchymal transition (EMT) and metastasis genes (SERPINE1, MMP-2, and IL-6), while BCCs co-cultured with leptin shRNA obASCs did not display similar levels of gene induction. Knockdown of leptin significantly reduced tumor volume and decreased the number of metastatic lesions to the lung and liver. These results correlated with reduced expression of both SERPINE1 and MMP-2 in tumors formed with MCF7 cells mixed with leptin shRNA obASCs, when compared to tumors formed with MCF7 cells mixed with control shRNA obASCs.

Conclusion

This study provides mechanistic insight as to how obesity enhances the proliferation and metastasis of breast cancer cells; specifically, obASC-derived leptin contributes to the aggressiveness of breast cancer in obese women.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0622-z) contains supplementary material, which is available to authorized users.

Role of leptin and leptin receptors in hematological malignancies

Leptin is an adipose-derived cytokine that has an important role in bodyweight homeostasis and energy balance. There are a number of studies which have suggested that leptin and its receptors dysregulation play a critical role in the development of malignancies including hematological malignancies, mainly via activation of the JAK/STAT pathway which regulates downstream signaling pathways such as PI3K/AKT signaling and ERK1/2. In this review, current understandings of leptin/leptin receptors mediated pathogenesis in various lymphoid malignancies are described. Blocking of the leptin receptor might be a unique therapeutic approach for many hematological malignancies.

Leptin, adipocytes and breast cancer: Focus on inflammation and anti-tumor immunity

More than one million new cases of breast cancer are diagnosed worldwide each year and more than 400,000 deaths are caused by the disease. The origin of this pathology is multifactorial and involved genetic, hormonal, environmental and nutritional factors including obesity in postmenopausal women. The role played by the adipose tissue and their secretions, ie adipokines, is beginning to be recognized. Plasma adipokine levels, which are modulated during obesity, could have “remote” effects on mammary carcinogenesis. Breast cancer cells are surrounded and locally influenced by an adipocyte microenvironment, which is probably more extensive in obese people. Hence, leptin appears to be strongly involved in mammary carcinogenesis and may contribute to the local pro-inflammatory mechanisms, especially in obese patients, who have increased metastatic potential and greater risk of mortality. This review presents the multifaceted role of leptin in breast cancer development and the different molecular pathways involved such as inflammation, oxidative stress and antitumor immunity.

Leptin exerts proliferative and anti-apoptotic effects on goose granulosa cells through the PI3K/Akt/mTOR signaling pathway

Leptin was known as a pivotal regulator for the control of food intake and energy expenditure. However, leptin has also been found to be involved in the regulation of female reproductive system through interactions with pathways in the hypothalamic-hypophyseal axis and direct action at the ovarian level. In the present study, granulosa cells from goose ovarian preovulatory (F1-F3) follicles were cultured with leptin (0, 1, 10 or 100ng/ml). The proliferative and anti-apoptotic actions of leptin in granulosa cells were revealed by CCK-8, BrdU and TUNEL assays. Quantitative real-time PCR and Western blot analyses further indicated that leptin treatment led to increased expression of cyclin D1, cyclin D2, cyclin D3 and bcl-2, and decreased expression of p21 and caspase-3. The effects were involved in the activation of the PI3K/Akt/mTOR signaling pathway, as leptin treatment enhanced the expression of PI3K, Akt1, Akt2, Raptor, mTOR, S6K and p-S6K. Moreover, blockade of the PI3K/Akt/mTOR pathway attenuated the influences of leptin on proliferation and apoptosis of granulosa cells, considering that activated factors by leptin were inhibited in the presence of either 20μM LY294002 (a PI3K inhibitor) or 10μM rapamycin (an mTOR inhibitor). In addition, leptin had a modulatory effect on the expression of its receptor at the transcriptional and translational levels, and blockade of PI3K/Akt/mTOR inhibited both basal and leptin-induced Lepr gene and protein expression. These findings suggest that leptin exerts its proliferative and anti-apoptotic effects on goose granulosa cells through the PI3K/Akt/mTOR signaling pathway via interaction with its receptor.

DICER1 regulated let-7 expression levels in p53-induced cancer repression requires cyclin D1

Let-7 miRNAs act as tumour suppressors by directly binding to the 3′UTRs of downstream gene products. The regulatory role of let-7 in downstream gene expression has gained much interest in the cancer research community, as it controls multiple biological functions and determines cell fates. For example, one target of the let-7 family is cyclin D1, which promotes G0/S cell cycle progression and oncogenesis, was correlated with endoribonuclease DICER1, another target of let-7. Down-regulated let-7 has been identified in many types of tumours, suggesting a feedback loop may exist between let-7 and cyclin D1. A potential player in the proposed feedback relationship is Dicer, a central regulator of miRNA expression through sequence-specific silencing. We first identified that DICER1 is the key downstream gene for cyclin D1-induced let-7 expression. In addition, we found that let-7 miRNAs expression decreased because of the p53-induced cell death response, with deregulated cyclin D1. Our results also showed that cyclin D1 is required for Nutlin-3 and TAX-induced let-7 expression in cancer repression and the cell death response. For the first time, we provide evidence that let-7 and cyclin D1 form a feedback loop in regulating therapy response of cancer cells and cancer stem cells, and importantly, that alteration of let-7 expression, mainly caused by cyclin D1, is a sensitive indicator for better chemotherapies response.

n-3 polyunsaturated fatty acids and mechanisms to mitigate inflammatory paracrine signaling in obesity-associated breast cancer

Globally, the prevalence of obesity is increasing which subsequently increases the risk of the development of obesity-related chronic diseases. Low-grade chronic inflammation and dysregulated adipose tissue inflammatory mediator/adipokine secretion are well-established in obesity, and these factors increase the risk of developing inflammation-associated cancer. Breast cancer is of particular interest given that increased inflammation within the subcutaneous mammary adipose tissue depot can alter the local tissue inflammatory microenvironment such that it resembles that of obese visceral adipose tissue. Therefore, in obese women with breast cancer, increased inflammatory mediators both locally and systemically can perpetuate inflammation-associated pro-carcinogenic signaling pathways, thereby increasing disease severity. Herein, we discuss some of these inflammation-associated pro-carcinogenic mechanisms of the combined obese breast cancer phenotype and offer evidence that dietary long chain n-3 polyunsaturated fatty acids (PUFA) may have utility in mitigating the severity of obesity-associated inflammation and breast cancer.

Leptin inhibits proliferation of breast cancer cells at supraphysiological concentrations by inhibiting mitogen-activated protein kinase signaling

Leptin is a hormone secreted by white fat tissue and signals the amount of overall body fat to the hypothalamus. The circulating concentration of leptin correlates with the level of obesity. Breast cancer risk is higher in obese postmenopausal women compared with postmenopausal women of a normal weight, and high leptin concentrations may contribute to this risk. In the present study, SK-BR-3 and MDA-MB-231 breast cancer cell lines were treated with various concentrations (6.25–1,600 ng/ml) of recombinant leptin and changes in cell proliferation were assessed. The SK-BR-3 breast cancer cells exhibited a concentration-dependent increase in proliferation with physiological leptin concentrations (<100 ng/ml), but no further increase in proliferation at high leptin concentrations (>100 ng/ml) was observed. Cell proliferation was not affected at supraphysiological leptin concentrations (>800 ng/ml) in SK-BR-3 cells, whereas it decreased in MDA-MB-231 cells. Therefore, cell signaling and cell cycle changes were assessed at supraphysiological concentrations (1,600 ng/ml). In the two cell lines, leptin treatment decreased the mitogen-activated protein kinase (MAPK) cell signaling pathway activation. Leptin treatment did not increase Akt phosphorylation or significantly alter the cell population distribution across cell cycle stages. To the best of our knowledge, leptin-induced growth inhibition of breast cancer cells at supraphysiological concentrations has not been reported in the literature to date, and the findings of this study suggest that reduced MAPK activity may be the underlying cause. Thus, the effect of leptin on breast cancer growth warrants further investigation since leptin is considered to be one of the main mediators in the obesity-breast cancer connection.

Leptin induces a proliferative response in breast cancer cells but not in normal breast cells

Obesity is a risk factor for breast cancer in postmenopausal women. Leptin, a hormone excessively produced during obesity, is suggested to be involved in breast cancer. The aim of the study was to investigate procarcinogenic potential of leptin by evaluating influence of leptin on cell proliferation, cell cycle, apoptosis, and signaling on numerous breast cells lines, including 184B5 normal cells, MCF10A fibrocystic cells and MCF-7, MDA-MB-231, and T47D cancer cells. Expressions of leptin and Ob-R were analyzed using qRT-PCR and immunohistochemistry, proliferation using fluorimetric resazurin reduction test and xCELLigence system, apoptosis and cell cycle by flow cytometry, and effect of leptin on different signalling pathways using qRT-PCR and Western blot. Cells were exposed to increasing concentrations of leptin. All cell lines expressed mRNA and protein of leptin and Ob-R. Leptin stimulated proliferation of all cell lines except for 184B5 and MDA-MB-231 cells. Leptin inhibited apoptosis but didn't alter proportion of cells within cell cycle in MCF7 cells. Leptin induced overexpression of leptin, Ob-R, estrogen receptor, and aromatase mRNA in MCF-7 and T47D cells. Autoregulation induced by leptin, relationship with estrogen pathway, and proliferative and antiapoptic activity in breast cancer cells may explain that obesity-associated hyperleptinemia may be a breast cancer risk factor.

Multifaceted leptin network: the molecular connection between obesity and breast cancer

High plasma levels of leptin, a major adipocytokine produced by adipocytes, are correlated with increased fat mass in obese state. Leptin is emerging as a key candidate molecule linking obesity with breast cancer. Acting via endocrine, paracrine, and autocrine manner, leptin impacts various stages of breast tumorigenesis from initiation and primary tumor growth to metastatic progression. Leptin also modulates the tumor microenvironment mainly through supporting migration of endothelial cells, neo-angiogenesis and sustaining recruitment of macrophage and monocytes. Various studies have shown that hyperactive leptin-signaling network leads to concurrent activation of multiple oncogenic pathways resulting in enhanced proliferation, decreased apoptosis, acquisition of mesenchymal phenotype, potentiated migration and enhanced invasion potential of tumor cells. Furthermore, the capability of leptin to interact with other molecular effectors of obese state including, estrogen, IGF-1, insulin, VEGF and inflammatory cytokines further increases its impact on breast tumor progression in obese state. This article presents an overview of the studies investigating the involvement of leptin in breast cancer.

Epigallocatechin gallate inhibits growth and epithelial-to-mesenchymal transition in human thyroid carcinoma cell lines

Well-differentiated papillary and follicular thyroid carcinoma are the most frequent types of thyroid cancer and the prognosis is generally favorable however, a number of patients develops recurrences. Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, was shown to possess remarkable therapeutic potential against various types of human cancers, although data on thyroid cancer cells are still lacking. The aim of this study was to investigate the effect of EGCG on the proliferation and motility of human thyroid papillary (FB-2) and follicular (WRO) carcinoma cell lines. Our results demonstrate that EGCG (10, 40, 60 μM) treatment inhibited the growth of FB-2 and WRO cells in a dose-dependent manner. These changes were associated with reduced cyclin D1, increased p21 and p53 expression. Furthermore, EGCG suppressed phosphorylation of AKT and ERK1/2. In addition EGCG treatment results in reduction of cell motility and migration. Changes in motility and migration in FB-2 were associated with modulation in the expression of several proteins involved in cell adhesion and reorganization of actin cytoskeleton. After 24 h EGCG caused an increase of the E-cadherin expression and a concomitant decrease of SNAIL, ZEB and the basic helix-loop-helix transcription factor TWIST. Besides expression of Vimentin, N-cadherin and α5-integrin was down-regulated. These data well correlate with a reduction of MMP9 activity as evidenced by gelatin zymography. Our findings support the inhibitory role of EGCG on thyroid cancer cell proliferation and motility with concomitant loss of epithelial-to-mesenchymal cell transition markers.

ERK1/2 inhibition enhances apoptosis induced by JAK2 silencing in human gastric cancer SGC7901 cells

Recent studies suggest JAK2 signaling may be a therapeutic target for treatment of gastric cancer (GC). However, the exact roles of JAK2 in gastric carcinogenesis are not very clear. Here, we have targeted JAK2 to be silenced by shRNA and investigated the biological functions and related mechanisms of JAK2 in GC cell SGC7901. In this study, JAK2 is commonly highly expressed in GC tissues as compared to their adjacent normal tissues (n = 75, p < 0.01). Specific down-regulation of JAK2 suppressed cell proliferation and colony-forming units, induced G2/M arrest in SGC7901 cells, but had no significant effect on cell apoptosis in vitro or tumor growth inhibition in vivo. Interestingly, JAK2 silencing-induced activation of ERK1/2, and inactivation of ERK1/2 using the specific ERK inhibitor PD98059 markedly enhanced JAK2 shRNA-induced cell proliferation inhibition, cell cycle arrest and apoptosis. Ultimately, combination of PD98059 and JAK2 shRNA significantly inhibited tumor growth in nude mice. Our results implicate JAK2 silencing-induced cell proliferation inhibition, cell cycle arrest, and ERK1/2 inhibition could enhance apoptosis induced by JAK2 silencing in SGC7901 cells.

Regulation of angiogenesis via Notch signaling in breast cancer and cancer stem cells

Breast cancer angiogenesis is elicited and regulated by a number of factors including the Notch signaling. Notch receptors and ligands are expressed in breast cancer cells as well as in the stromal compartment and have been implicated in carcinogenesis. Signals exchanged between neighboring cells through the Notch pathway can amplify and consolidate molecular differences, which eventually dictate cell fates. Notch signaling and its crosstalk with many signaling pathways play an important role in breast cancer cell growth, migration, invasion, metastasis and angiogenesis, as well as cancer stem cell (CSC) self-renewal. Therefore, significant attention has been paid in recent years toward the development of clinically useful antagonists of Notch signaling. Better understanding of the structure, function and regulation of Notch intracellular signaling pathways, as well as its complex crosstalk with other oncogenic signals in breast cancer cells will be essential to ensure rational design and application of new combinatory therapeutic strategies. Novel opportunities have emerged from the discovery of Notch crosstalk with inflammatory and angiogenic cytokines and their links to CSCs. Combinatory treatments with drugs designed to prevent Notch oncogenic signal crosstalk may be advantageous over λ secretase inhibitors (GSIs) alone. In this review, we focus on the more recent advancements in our knowledge of aberrant Notch signaling contributing to breast cancer angiogenesis, as well as its crosstalk with other factors contributing to angiogenesis and CSCs.

Cooperation of bisphenol A and leptin in inhibition of caspase-3 expression and activity in OVCAR-3 ovarian cancer cells

This study was designed to investigate the effect of bisphenol A and leptin on caspase-3 expression and activity in OVCAR-3 ovarian cancer cells. Caspase-3 and survivin expression was measured at the transcript level by real-time PCR and at the protein level by Western blotting. In addition, caspase-3 activity was measured, using a fluorometric assay, upon exposure to bisphenol A (40 nM) alone, leptin (2.5 nM) alone, and the combination of both agents. 17β-estradiol (40 nM) was used as a positive control for estrogenic properties of bisphenol A. Results showed that the interaction between bisphenol A and leptin, which was similar to that observed between 17β-estradiol and leptin, led to the inhibition of caspase-3 expression and activity in OVCAR-3 cells. Surprisingly, survivin was found to not be involved in the anti-apoptotic activity of either agent. Also, results showed that leptin inhibits caspase-3 activity by acting on the signal transducers and activators of transcription 3 (STAT3) pathway, but bisphenol A and 17β-estradiol by the extracellular-signal-regulated kinases 1/2 (ERK1/2) pathway. In conclusion, the study reveals that bisphenol A and leptin interact to inhibit caspase-3 expression and activity by modulating STAT3 and ERK1/2 signaling pathways in OVCAR-3 cells.

Obesity, independent of p53 gene dosage, promotes mammary tumor progression and upregulates the p53 regulator microRNA-504

Obesity, prevalent in >35% of US women, is an established risk and progression factor for postmenopausal breast cancer, and strategies to break the obesity-breast cancer link are urgently needed. Approximately 30% of breast cancers carry p53 tumor suppressor gene alterations; however, the effects of obesity on breast cancer progression in relation to p53 gene dosage are unclear. Using murine models of postmenopausal breast cancer, we characterized the interactive effects of diet-induced obesity (DIO) and p53 gene dosage on mammary tumor growth and associated p53-related regulatory mechanisms. Ovariectomized C57BL/6 mice were randomly assigned to receive a DIO or control diet, and (at 10 weeks) orthotopic injection of MMTV-Wnt-1 p53^+/− or MMTV-Wnt-1 p53^+/+ mammary tumor cells (n = 20 mice per diet and genotype group). DIO and control diets produced distinct phenotypes (mean percent body fat at 10 weeks: 57% and 39%, respectively, P<0.001). Regardless of phenotype, time to first palpable tumor was 57% less for Wnt-1 p53^+/− than Wnt-1 p53^+/+ tumors. Regardless of tumoral p53 genotype, DIO (relative to control) increased tumor burden, tumor cell proliferation (Ki-67), severity of tumor pathology, local tissue invasion, epithelial-to-mesenchymal transition (EMT) programming, and tumoral microRNA-504 (a negative regulator of p53) expression; and suppressed p53, p21, and estrogen receptor-alpha protein expression. These findings in murine models of postmenopausal breast cancer suggest that obesity may augment procancer effects related to p53 gene alterations. Furthermore, microRNA-504, an obesity-responsive negative regulator of p53 and putative EMT regulator, may represent a novel molecular target for breaking the obesity-breast cancer link.

[Leptin: Involvement in the pathophysiology of breast cancer]

More than one million new cases of breast cancer are diagnosed each year worldwide and more than 400,000 deaths occur due to this pathology. Obesity is a risk factor for postmenopausal breast cancer and the place held by the adipose tissue and secretions (i.e. adipokines) begins to be recognized. Indeed, firstly, plasma adipokine levels, modulated in obesity situation, could have effects "remotely" on mammary carcinogenesis and, secondly, breast cancer cells are surrounded by adipocyte microenvironment, which is probably more important in the case of obesity, and may be locally influenced by it. In this context, leptin appears to be strongly involved in mammary carcinogenesis and may contribute to the angiogenesis process and local pro-inflammatory mechanisms, especially in obese patients for whom increased metastatic potential and risk of mortality are described.

Leptin stimulation of cell cycle and inhibition of apoptosis gene and protein expression in OVCAR-3 ovarian cancer cells

The OVCAR-3 cell line expressing the long (ObRb) and short (ObRt) isoforms of leptin receptor mRNA was used to analyze the effect of leptin on the expression of selected genes and proteins involved in the cell cycle and apoptosis. OVCAR-3 cells were exposed to 2, 20, 40, and 100 ng/ml of leptin. Cell proliferation was determined using the alamarBlue cell viability test and flow cytometry. Apoptosis was measured using a cellular DNA fragmentation ELISA kit. The expression of selected cell cycle and apoptosis genes was evaluated by real-time PCR and confirmed by western blot. The stimulatory action of leptin on cell proliferation was observed as an increase in cells in the S and G2/M phases. Up-regulation of genes responsible for inducing cell proliferation and suppression of genes responsible for inhibition of proliferation were noted. Western blots revealed increased expression of cyclins D and A and inhibition of p21WAF1/CIP1 protein expression by leptin. Inhibition of DNA fragmentation was observed under all leptin doses. Suppression of genes involved in the extrinsic and intrinsic apoptotic pathway was observed. Western blots illustrated decreased Bad, TNFR1, and caspase 6 protein expression in response to leptin treatment. Leptin promotes ovarian cancer cell line growth by up-regulating genes and proteins responsible for inducing cell proliferation as well as down-regulating pro-apoptotic genes and proteins in apoptotic pathways. Results of this study warrant examining the relationship between the risk of ovarian cancer and elevated leptin levels in obese women.

Breast cancer and obesity: in vitro interferences between adipokines and proangiogenic features and/or antitumor therapies?

Obesity is now considered as a risk factor for breast cancer in postmenopausal women. Adipokine levels are modulated in obesity, and may play a role in carcinogenesis. Moreover, obesity increases risk of cancer mortality. Here, we hypothesized that this increase could be due to a modification in angiogenesis, capital event in the development of metastases, and/or in effectiveness of cancer treatments. To test these assumptions, following a same experimental design and simultaneously the effects of leptin and adiponectin on angiogenesis were investigated, and the impact of hyperleptinemia on anticancer drug effectiveness was measured in physiological and obesity situations. Focusing on angiogenesis, the proliferation of endothelial cells (HUVEC), which expressed leptin and adiponectin receptors, was stimulated by leptin and inhibited by adiponectin. Both adipokines globally reduced apoptosis and caspase activity. Leptin increased migration whereas adiponectin decreased migration, and leptin enhanced the area of the tubes formed by HUVEC cells while adiponectin inhibited their formation. MCF7 and MDA-MB-231 cells treated with leptin secreted more VEGF than untreated cells, whereas adiponectin treatment inhibited VEGF secretion. Finally, MCF7 cells pre-treated with leptin were more invasive than untreated cells. This effect was not reproduced in MDA-MB-231 cells. In the MCF7 breast cancer cell line, leptin could induce cell proliferation and reduced the efficacy of all breast cancer therapies (tamoxifen, 5-fluorouracil, taxol and vinblastin). These results suggest that, in obesity situation, leptin– in contrast to adiponectin – may promote tumor invasion and angiogenesis, leading to metastases ‘apparition, and reduce treatment efficacy, which could explain the increased risk of cancer mortality in cases of overweight. The evidence suggests adipokines influence breast cancer issue and could play a significant role, especially in obese patients for which hyperleptinemia, hypoadiponectinemia and increased metastatic potential are described.

Clinicopathological implications of leptin and leptin receptor expression in papillary thyroid cancer

The role of leptin and its receptors (OBRs) in the pathogenesis of various primary human malignancies has been demonstrated. However, their expression and clinicopathological significance in papillary thyroid cancer (PTC) is not fully understood. In this study, we examined the expression of leptin and OBRs in 76 PTC samples using immunohistochemistry, and their associations with clinicopathological parameters were evaluated. The expression of OBRs was observed in the tumor cell membrane and/or cytoplasm, with a positive rate of 73.7% (56/76), while leptin was expressed in the tumor cell cytoplasm in 55 of 76 cases (72.4%). The expression of either protein was associated with greater tumor size (P=0.016 for leptin and P=0.002 for OBRs). In addition, the expression levels of leptin and OBRs were associated with each other. Neither leptin nor OBR expression levels were associated with other parameters, including age, body weight, postmenopausal state, multifocality and lymph node metastasis. These data suggest that the expression of leptin and/or OBRs in PTC is associated with tumor size and may be a potential target in PTC.

Leptin stimulates ovarian cancer cell growth and inhibits apoptosis by increasing cyclin D1 and Mcl-1 expression via the activation of the MEK/ERK1/2 and PI3K/Akt signaling pathways

Obesity is known to be an important risk factor for many types of cancer, such as breast, prostate, liver and endometrial cancer. Recently, epidemiological studies have indicated that obesity correlates with an increased risk of developing ovarian cancer, the most lethal gynecological cancer in developed countries. Leptin is predominantly produced by adipocytes and acts as a growth factor and serum leptin levels positively correlate with the amount of body fat. In this study, we investigated the effects of leptin on the growth of ovarian cancer cells and the underlying mechanism(s) of action. Our results showed that leptin stimulated the growth of the OVCAR-3 ovarian cancer cell line using MTT assay and trypan blue exclusion. Using western blot analysis, we found that leptin enhanced the expression of cyclin D1 and Mcl-1, which are important regulators of cell proliferation and the inhibition of apoptosis. To investigate the signaling pathways that mediate the effects of leptin, cells were treated with leptin plus specific inhibitors of JAK2, PI3K/Akt and MEK/ERK1/2 and analysis of the phosphorylation state of proteins was carried out by western blot assays. We showed that the activation of the MEK/ERK1/2 and PI3K/Akt signaling pathways were involved in the growth-stimulating effect of leptin on ovarian cancer cell growth and the specific inhibitors of PI3K/Akt and MEK/ERK1/2 revealed that these two pathways interacted with each other. Our data demonstrate that leptin upregulates the expression of cyclin D1 and Mcl-1 to stimulate cell growth by activating the PI3K/Akt and MEK/ERK1/2 pathways in ovarian cancer.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

The association of a variant in the cell cycle control gene CCND1 and obesity on the development of asthma in the Swiss SAPALDIA study

OBJECTIVE

The molecular mechanisms underlying the association between obesity (BMI ≥ 30 kg/m(2)) and asthma are poorly understood. Since shifts in the fate of bronchial cells due to low-grade systemic inflammation may provide a possible explanation, we investigated whether two of the best documented functional variants in cell cycle control genes modify the obesity-asthma association.

METHODS

We genotyped 5930 SAPALDIA cohort participants for the single-nucleotide polymorphisms (SNPs) rs9344 in the cyclin D1 gene (CCND1) and rs1042522 in the gene encoding tumor protein 53 (TP53). We assessed the independent association of these SNPs and obesity with asthma prevalence and incidence.

RESULTS

The CCND1 SNP modified the association between obesity and asthma prevalence (p(interaction )= 0.03). The odds ratios (ORs) and 95% confidence intervals (CIs) for reporting a physician diagnosis of asthma at baseline, comparing obese with non-obese participants, were 1.09 (0.51-2.33), 1.64 (0.94-2.88), and 3.51 (1.63-7.53) for GG, GA, and AA genotypes, respectively. We found comparable genotype differences for incident asthma within the 11 years of follow-up. As for the TP53 SNP, the interactions with obesity status with respect to asthma were not statistically significant.

CONCLUSIONS

Our results suggest that obesity may contribute to asthma and associated tissue remodeling by modifying the processes related to the CCND1 gene activity.